Simulated Damage Research Articles

Simulation and experimental study of tool wear and damage in milling SA 508III steel

SA 508III steel is a typical difficult-to-machine material with high strength and high-temperature mechanical properties. In the milling process, the carbide tool is seriously damaged and their service life is short under the thermal-mechanical load of low cycle and high impact. In this paper, firstly, the finite element simulation of milling SA 508III steel is carried out to study the characteristics of thermal-mechanical load and tool wear during milling. Secondly, the wear experiment of cemented carbide tools is carried out. The morphology changes of the rake face and flank face of cemented carbide tools are observed and analyzed. The nature of tool wear and damage is discussed. Finally, the rule of crack development from microscopic defects to macroscopic cracks until tool fracture is described, and the tool failure mechanism is explored. The research results can provide theoretical basis and technical support for the optimal design of cutting tools of high-efficiency milling SA 508III steel and the improvement of cutting performance and service life of tools.

Analysis of displacement damage mechanism and simulation proton irradiation on GaAs

GaAs is an important material for preparing power supply for space vehicles, satellites, and space systems. To study the displacement damage of GaAs material caused by protons in the space environment, in this article, the Monte Carlo software Geant4 was used to simulate the transport process of space protons in GaAs; calculate the non-ionizing energy loss (NIEL) of protons with different energies; and obtain the species, energy range, and proportion of primary knock-on atom produced by proton irradiation with different energies. The results show that with the increase in the incident proton energy, the probability of elastic collision decreases and the probability of inelastic collision increases. The main source of displacement damage changes from elastic collision to inelastic collision. The radiation damage of low energy protons is serious at the end of the range, while that of high energy protons is serious at the beginning and end of the range. With the increase in the proton energy, the number of displaced atoms increases and the NIEL changes slowly. This provides a theoretical reference for the reliable operation of spacecraft.

Chemical ordering effect on the radiation resistance of a CoNiCrFeMn high-entropy alloy

The chemical ordering of CoNiCrFeMn and its effect on radiation resistance is analyzed in this study via Monte Carlo (MC) annealing simulation and molecular dynamics (MD) radiation damage simulation. MC annealing at a lower temperature of 600 K forms an initial stage Cr-rich region in CoNiCrFeMn due to a strong chemical ordering-driven phase decomposition; whereas, annealing at a higher temperature of 1100 K forms a chemical short-range order (CSRO). MD radiation damage simulation shows that the Cr-rich region formed by 600 K annealing accelerates the aggregation and the evolution of defects, facilitating more dislocation loops formation. On the other hand, the CSRO structure formed by 1100 K annealing effectively delays the growth of defect number and tends to reduce the dislocation density and defect diffusion, suggesting better radiation resistance. However, the CSRO structure is destroyed by radiation, thus these advantages of CSRO will disappear in due time if CSRO cannot heal. Fortunately, since the CSRO can recover at working temperature of 1100 K, we speculate that under the working temperature of 1100 K and with a modest radiation damage rate, the advantages of CSRO can maintain for a long time. We finally discuss the condition of the CSRO preservation by proposing a CSRO radiation damage – diffusion healing competition model.

An Innovative Structural Damage Detection System for Preventive Maintenance of Wind Turbines

This study aims to develop a novel damage detection and preventive maintenance system that can be used for continuous or periodic monitoring of wind turbine components. The main features of the proposed system such as the measurement technique, data analysis procedure, and damage estimation methodology are described in detail by presenting the results of finite element model-based damage simulations, laboratory experiments, and in-field vibration tests. A hybrid measurement system with accelerometers and an automated infrared laser scanner is used to acquire vibration data with high spatial resolution. The obtained response data are then processed to extract the dynamic properties (e.g., natural vibration periods and mode shapes) of the structure. An efficient damage detection algorithm, which is based on monitoring sudden changes observed in mode shapes, is utilized to determine the location and extent of a possible damage. Within the scope of the work, a novel and simplified version of the widely used mode shape curvature method is developed for the rapid analysis and interpretation of the acquired vibration data. The applicability of the proposed methodology is demonstrated on a 61.5 m long numerical blade model proposed for NREL 5 MW Benchmark wind turbine.

Modelling damage in half-hole pin bearing cross-ply and angle-ply composite laminates

This paper presents the development and validation of a mesoscale numerical model to predict the bearing failure of composite laminates reinforced by unidirectional continuous fibers, focusing on specimens that show a significant non-linear response prior to failure. Half-hole pin bearing tests were carried out with multiple instrumentation for the comprehensive characterization of the failure process. Three-dimensional finite element models were used for the simulation of plastic deformation and damage of the cross- and angle-ply specimens using fiber-aligned mesh for the composite plies. To consider the non-linear material behavior prior to crack propagation, the constitutive model proposed includes a bi-linear elastoplastic model to represent the non-linear response under longitudinal shear. For the prediction of the peak and post-peak behavior, 3D invariant-based failure criteria and mechanism-based continuum damage models were used for intralaminar damage, together with a discrete cohesive zone model for delamination. Thorough analyses and comparisons of the experimental and numerical results show a good correlation of the bearing strengths and overall deformation, as well as good agreement in terms of damage size and damage shape. Relevant limitations include difficulties in predicting the post-peak plateau stresses and the loading displacements in some configurations, setting the stage for additional future research.

Mesoscopic numerical study on ductile fracture in TRIP steel under reverse loading

The aim of this study is to elucidate the fracture mechanism of transformation-induced plasticity (TRIP) steel under reverse loading using a ductile damage simulation method. First, the fracture limit of a TRIP steel under the reverse path is experimentally investigated and compared with the results of a dual-phase (DP) steel without a retained austenite. In both steels, the reduction in fracture strain by compressive pre-strain is smaller than that by tensile pre-strain. The difference between the effects of tensile and compressive pre-strain is even larger in the TRIP steel than in the DP steel. These results are analyzed via numerical calculations using a model that extends the ductile damage theory proposed by Ohata et al. to account for the microstructural changes caused by martensitic transformation. The results indicate that the development of damage in the TRIP steel strongly depends on the fraction and distribution of the hard martensite generated by the transformation. Moreover, when TRIP steels are subjected to compressive pre-strain, martensitic transformation occurs less likely than when they are subjected to tensile pre-strain. This leads to less heterogeneity and less void formation within the microstructure. As a result, the fracture strain decrease in TRIP steel due to compressive pre-strain is smaller than that in DP steel.

Strain-Field Modifications in the Surroundings of Impact Damage of Carbon/Epoxy Laminate.

The relationship between deformation and stress is crucial for any elasto-plastic body. This paper deals with the experimental identification of the basic parameters of the composite laminate model in relation to the finite element model. Standardized tensile, impact, and post-impact tests on a carbon fiber-reinforced epoxy laminate were used. The method by which the elasticity and failure parameters were obtained from the initial components is described. In the article, the modes of initiation and complete failure of samples in tensile tests, which are compared with the simulation, are presented. Furthermore, the article deals with the issue of the generation and detection of damage by low-speed impact, which can be caused by contact with moving objects, due to improper handling or maintenance. The results of impact analysis simulations are shown in the context of strain-field distribution changes obtained with the help of digital image correlation. The results showed high agreement between the calculations and the experiments. Based on this agreement, simulations of impact damage for various energies were performed. These simulations were used to determine the approximate sizes of the affected zones in relation to the impact energy. The results are finally discussed in the context of the possible use of structural health monitoring based on strain modifications.

A Damage Model of Concrete including Hysteretic Effect under Cyclic Loading.

A novel damage model for concrete has been developed, which can reflect the complex hysteresis phenomena of concrete under cyclic loading, as well as other nonlinear behaviors such as stress softening, stiffness degradation, and irreversible deformation. The model cleverly transforms the complex multiaxial stress state into a uniaxial state by equivalent strain, with few computational parameters and simple mathematical expression. The uniaxial tensile and compressive stress–strain curves matching the actual characteristics are used to accommodate the high asymmetry of concrete in tension and compression, respectively. Meanwhile, an unloading path and a reloading path that can reflect the hysteresis effect under cyclic loading of concrete are established, in which the adopted expressions for the loading and unloading characteristic points do not depend on the shape of the curve. The proposed model has a concise form that can be easily implemented and also shows strong generality and flexibility. Finally, the reliability and correctness of the model are verified by comparing the numerical results with the three-point bending beam test, cyclic loading test, and a seismic damage simulation of the Koyna gravity dam.

Formation damage simulation of a multi-fractured horizontal well in a tight gas/shale oil formation

Formation damage in drilling comes from drilling fluid invasion due to high differential pressure between a wellbore and the formation. This mechanism happens with fracture fluid invasion of multi-fractured horizontal wells in tight formations. Some multi-fractured wells show production rates and cumulative productions far lower than expected. Those damaged wells may sustain further impact such as well shutting due to unexpected events such as the COVID-19 outbreak and then experience a further reduction in cumulative production. This paper focuses on the root causes of formation damage of fractured wells and provides possible solutions to improve production. A simulation study was conducted using Computer Modelling Group software to simulate formation damage due to fracture fluid invasion and well shut-in. Simulation results revealed that the decrease in cumulative hydrocarbon production due to leak-off and shut-in of the simulated well could range from 20 to 41%, depending on different conditions. The results showed that the main causes are high critical water saturation of tight formations, low drawdown, and low residual proppant permeability under formation closure stress. The sensitivity analysis suggests two feasible solutions to mitigate formation damage: optimizing drawdown during production and optimized proppant pack permeability of the hydraulic fracturing process. Optimizing pressure drawdown is effective in fixing leak-off damage, but it does not mitigate shut-in damage. Formation damage due to shut-in should be prevented in advance by using an appropriate proppant permeability. These key findings enhance productivity and improve the economics of tight gas and shale oil formations.

A novel methodology to research the residual compressive mechanical properties of composite stiffened panel after low velocity impact based on quantification damage simulation

AbstractComposite stiffened panels have become one of the most usual components in the design process of the aircraft's structure due to their splendid mechanical properties in the last decades. The main purpose of this work is investigating and presenting a more precise method to forecast the residual compressive mechanical behavior of the composite stiffened panel. First of all, an axial compression after impact (CAI) test is performed to understand the failure mechanism of different type of L‐shaped stiffened carbon fiber reinforced polymer panels with barely visible impact damage, which is introduced by the low velocity impact test. Subsequently, a finite element model, which contains a quantification damage model, is established in ABAQUS software based on the CAI test results to predict the mechanical behavior of these composite stiffened panels during the CAI test process. Both of the experimental and predicted results demonstrate that the propagation of the delamination caused by LVI is going to exert a destructive influence on the total failure of the composite stiffened panel, and the prediction results of the residual compressive strength of these composite stiffened panels are well consistent to that measured in the CAI test.

Tree crown damage and its effects on forest carbon cycling in a tropical forest.

Crown damage can account for over 23% of canopy biomass turnover in tropical forests and is a strong predictor of tree mortality; yet, it is not typically represented in vegetation models. We incorporate crown damage into the Functionally Assembled Terrestrial Ecosystem Simulator (FATES), to evaluate how lags between damage and tree recovery or death alter demographic rates and patterns of carbon turnover. We represent crown damage as a reduction in a tree's crown area and leaf and branch biomass, and allow associated variation in the ratio of aboveground to belowground plant tissue. We compare simulations with crown damage to simulations with equivalent instant increases in mortality and benchmark results against data from Barro Colorado Island (BCI), Panama. In FATES, crown damage causes decreases in growth rates that match observations from BCI. Crown damage leads to increases in carbon starvation mortality in FATES, but only in configurations with high root respiration and decreases in carbon storage following damage. Crown damage also alters competitive dynamics, as plant functional types that can recover from crown damage outcompete those that cannot. This is a first exploration of the trade-off between the additional complexity of the novel crown damage module and improved predictive capabilities. At BCI, a tropical forest that does not experience high levels of disturbance, both the crown damage simulations and simulations with equivalent increases in mortality does a reasonable job of capturing observations. The crown damage module provides functionality for exploring dynamics in forests with more extreme disturbances such as cyclones and for capturing the synergistic effects of disturbances that overlap in space and time.

A Review on DPA for computing radiation damage simulation

A Monte Carlo code is developed for the radiation damage in the metals which results from nuclear collisions that create energetic recoil atoms of the host material. The development of the simulation codes for the radiation damage method by neutrons and protons can be highly useful in technology of advanced nuclear systems and nuclear fusion reactors. The aim of this review is to investigate the impact of the radiation damage in the materials by the neutron and proton energy irradiation. The damage parameter used in the evaluation is displacement per atom (DPA) in material as a function of neutron and proton energy. For this purpose, there are some software codes used which are related to radiation damage because radiation damage can be measured as a function of DPA, which is one of the critical issues for high intensity beams, particularly, for protons and neutrons.

TOPAS-nBio simulation of temperature-dependent indirect DNA strand break yields

Current Monte Carlo simulations of DNA damage have been reported only at ambient temperature. The aim of this work is to use TOPAS-nBio to simulate the yields of DNA single-strand breaks (SSBs) and double-strand breaks (DSBs) produced in plasmids under low-LET irradiation incorporating the effect of the temperature changes in the environment. A new feature was implemented in TOPAS-nBio to incorporate reaction rates used in the simulation of the chemical stage of water radiolysis as a function of temperature. The implemented feature was verified by simulating temperature-dependent G-values of chemical species in liquid water from 20 °C to 90 °C. For radiobiology applications, temperature dependent SSB and DSB yields were calculated from 0 °C to 42 °C, the range of available published measured data. For that, supercoiled DNA plasmids dissolved in aerated solutions containing EDTA irradiated by Cobalt-60 gamma-rays were simulated. TOPAS-nBio well reproduced published temperature-dependent G-values in liquid water and the yields of SSB and DSB for the temperature range considered. For strand break simulations, the model shows that the yield of SSB and DSB increased linearly with the temperature at a rate of (2.94 ± 0.17) × 10−10 Gy–1 Da–1 °C–1 (R 2 = 0.99) and (0.13 ± 0.01) × 10−10 Gy–1 Da–1 °C–1 (R 2 = 0.99), respectively. The extended capability of TOPAS-nBio is a complementary tool to simulate realistic conditions for a large range of environmental temperatures, allowing refined investigations of the biological effects of radiation.

Development and Application of a Platform for Multidimensional Urban Earthquake Impact Simulation

Earthquakes can be devastating to cities. Therefore, accurate and efficient simulation of the potential seismic damage to buildings has become an indispensable part of worldwide efforts to mitigate earthquake hazards. Precise simulation results can highlight potential seismic damage and serve as a reference in urban development and for planning post-earthquake rescue operations. In urban areas, simulation of the structural dynamic response during an earthquake is key for planning an appropriate emergency response. Multidimensional visualization of the effects of earthquakes is a popular technique in current earthquake simulation research. In the present study, a dynamic multidimensional simulation method was developed for analyzing the impact of an earthquake on buildings. This method involved conducting three-dimensional (3D) dynamic analysis of data from a seismic capacity database. Polygonal models and seismic capacity data were used in a high-performance computing process to calculate the seismic response of each building in an urban environment. On the basis of the calculations, a platform was developed for multidimensional urban earthquake impact simulation (MDUES). The developed MDUES platform enables analysis of the impact of long-period earthquakes, simulation of the 3D seismic responses of buildings, and visualization of the disaster risk and earthquake impact in a specified area. In summary, simulation of structural seismic responses in an urban setting necessitates a careful examination of the characteristics of ground and building motion, and the results of this simulation can provide a crucial reference for city planning, post-earthquake rescue operations, and seismic damage assessments.

Simulation of radiation damage via alpha decay in BFS:PC grouts using 4He2+ ion acceleration

The impact of alpha radiation on cements used to encapsulate intermediate-level waste (ILW) is not well understood. ILW wastes can contain high levels of alpha-emitting radionuclides, meaning that the grouts used to encapsulate them are exposed to significant ionising radiation. Thus, a damaged region could develop in the grout adjacent to the alpha-emitting species. This work attempted to recreate this behaviour through nonradioactive 4He2+ ion-accelerator experiments, which have not previously been applied to common encapsulation grouts. The influence of this irradiation on a slag-Portland cement was investigated at different ages via transmission electron microscopy energy-dispersive x-ray spectroscopy (TEM-EDX) and supporting techniques, to assess whether 4He2+ irradiation caused textural or chemical zonation. No significant changes in hydrate phases or textures were observed, other than minor variations associated with carbonation. This paper provides a proof of concept for using ion acceleration techniques on cements and furthers knowledge on their radiation response.

Structure Damage Identification Based on Information Entropy and Bayesian Fusion

When processing signals, information entropy theory and data fusion theory have their own advantages. The former can improve the sensitivity of signals, while the latter can superimpose multisource information to correct system deviations and obtain the best identification results. Therefore, we introduce two theories into structural damage identification to improve the reliability of damage identification. First, based on the modal strain energy damage identification index, combined with information entropy and data fusion theory, a fusion entropy index (FE) and an entropy weight fusion index (EWF) are constructed. Then, the simply supported beam and truss structure model are established for damage simulation, which verified that the FE index and EWF index can accurately locate the damage. The polynomial fitting method is used to identify the damage degree of the structure, and the identification results obtained are more accurate. Finally, a simple-supported steel beam model is established in the laboratory for verification and analysis. The results show that the proposed FE index and EWF index have high damage sensitivity, noise resistance, and robustness, and relatively speaking, EWF index damage recognition ability is better. The method proposed in this paper provides an empirical method for practical engineering application.

Impact of DNA Geometry and Scoring on Monte Carlo Track-Structure Simulations of Initial Radiation-Induced Damage.

Track structure Monte Carlo simulations are a useful tool to investigate the damage induced to DNA by ionizing radiation. These simulations usually rely on simplified geometrical representations of the DNA subcomponents. DNA damage is determined by the physical and physicochemical processes occurring within these volumes. In particular, damage to the DNA backbone is generally assumed to result in strand breaks. DNA damage can be categorized as direct (ionization of an atom part of the DNA molecule) or indirect (damage from reactive chemical species following water radiolysis). We also consider quasi-direct effects, i.e., damage originated by charge transfers after ionization of the hydration shell surrounding the DNA. DNA geometries are needed to account for the damage induced by ionizing radiation, and different geometry models can be used for speed or accuracy reasons. In this work, we use the Monte Carlo track structure tool TOPAS-nBio, built on top of Geant4-DNA, for simulation at the nanometer scale to evaluate differences among three DNA geometrical models in an entire cell nucleus, including a sphere/spheroid model specifically designed for this work. In addition to strand breaks, we explicitly consider the direct, quasi-direct, and indirect damage induced to DNA base moieties. We use results from the literature to determine the best values for the relevant parameters. For example, the proportion of hydroxyl radical reactions between base moieties was 80%, and between backbone, moieties was 20%, the proportion of radical attacks leading to a strand break was 11%, and the expected ratio of base damages and strand breaks was 2.5-3. Our results show that failure to update parameters for new geometric models can lead to significant differences in predicted damage yields.

Simulation of buckling-driven progressive damage in composite wind turbine blade under extreme wind loads

Wind turbine blades are continuously upscaled in size to meet the increasing demand of low cost renewable energy. The larger and slender blades with reduced mass are susceptible to large-deflection bending and instability during extreme wind gusts. The loading can induce interactive damage modes such as adhesive bond failure and composite skin damage progressively degrading the blade structural performance. The structural deformation and instability as well as progressive damage in composite blade is analyzed by developing finite element (FE) models using ANSYS software. First, a geometric nonlinear FE analysis of the 3D blade is performed to predict its deflection and regions of high stresses. The results demonstrated that high compressive stresses in the blade suction side trigger local skin buckling; thus initiating debonding of weak adhesive interface joint between skin and spar combined with skin damage. Subsequently, the interactive buckling-driven skin-spar debonding and composite skin damage in the identified region are analyzed through a submodel using cohesive zone model (CZM) as well as continuum damage mechanics (CDM) based progressive failure analysis, respectively, through a user-defined material subroutine. The results indicated that buckling-driven debonding of adhesive interface between skin and spar was primary damage mode leading to progressive failure of the blade composite skin. Consequently, the blade ultimate load carrying-ability was governed by coupled adhesive debonding and progressive skin damage phenomena, which is in good agreement with published experimental results. The developed simulation approach is capable to efficiently analyze the interactive buckling-induced interface damage as well as progressive failure of composite blade structure. In this work, modelling of interaction between interface debonding and skin damage, based on the CZM and CDM scheme, is a novel methodology for progressive damage analysis of blade under extreme loading.

Mesoscale simulation of frost damage to rock material based on Rigid Body Spring Method

Frost damage is one of the most important deterioration factors for porous materials in cold and wet region. In this study, a mesoscale numerical study is conducted to estimate the frost damage of rock materials based on the Rigid Body Spring Method. The mesoscale elastoplastic constitutive law is presented cooperated with the ice formation model for the rock material. Then, the cyclic expansion of selected marble during multiple freeze-thaw cycles (FTC) is simulated, resulting in different values of residual strain. It is found that using the residual strain as a link between freezing process and mechanical degradation, the damaged compressive behaviors after different numbers of FTC can be successfully explained and reproduced, including the crack recovery phenomenon. The findings in this study are beneficial for the further simulation of frost deterioration history, considering the large variability in properties of rock material.

A Monte Carlo study of the relative biological effectiveness in surface brachytherapy.

This work aims to simulate clustered DNA damage from ionizing radiation and estimate the relative biological effectiveness (RBE) for radionuclide (rBT)- and electronic (eBT)-based surface brachytherapy through a hybrid Monte Carlo (MC) approach, using realistic models of the sources and applicators. Damage from ionizing radiation has been studied using the Monte Carlo Damage Simulation algorithm using as input the primary electron fluence simulated using a state-of-the-art MC code, PENELOPE-2018. Two 192 Ir rBT applicators, Valencia and Leipzig, one 60 Co source with a Freiburg Flap applicator (reference source), and two eBT systems, Esteya and INTRABEAM, have been included in this study implementing full realizations of their geometries as disclosed by the manufacturer. The role played by filtration and tube kilovoltage has also been addressed. For rBT, an RBE value of about 1.01 has been found for the applicators and phantoms considered. In the case of eBT, RBE values for the Esteya system show an almost constant RBE value of about 1.06 for all depths and materials. For INTRABEAM, variations in the range of 1.12-1.06 are reported depending on phantom composition and depth. Modifications in the Esteya system, filtration, and tube kilovoltage give rise to variations in the same range. Current clinical practice does not incorporate biological effects in surface brachytherapy. Therefore, the same absorbed dose is administered to the patients independently on the particularities of the rBT or eBT system considered. The almost constant RBE values reported for rBT support that assumption regardless of the details of the patient geometry, the presence of a flattening filter in the applicator design, or even significant modifications in the photon energy spectra above 300keV. That is not the case for eBT, where a clear dependence on the eBT system and the characteristics of the patient geometry are reported. A complete study specific for each eBT system, including detailed applicator characteristics (size, shape, filtering, among others) and common anatomical locations, should be performed before adopting an existing RBE value.